CHICAGO -- Amid the cold world's uncertainties, there is the comfort of having one incontrovertible axiom: If something seems too good to be true, it isn't true. Something, or someone.

Then along comes Jack Ryan.

Six-foot-four and Hollywood handsome, he grew up in this city's northern suburbs, graduated from Dartmouth, simultaneously earned degrees from Harvard's law and business schools, then was made partner at Goldman Sachs where he made a bundle. The man who made him partner, Jon Corzine, made a mega-bundle, ran successfully for Senate from New Jersey, and in this election cycle is chairman of the Democratic Senatorial Campaign Committee, charged with defeating Republican senate candidates.

Three years ago, when Ryan was 41, he walked away from moneymaking to start his real life. Or resume it. Earlier he had been doing what his family has always done, which involves making the rest of us seem like moral slackers.

Ryan, who keeps in moral and physical trim by going to mass and the gym each morning, left Goldman Sachs to become a teacher at Hales Franciscan High School in the heart of the huge African-American community on the South Side. In an area where some schools send more young men to prison than to college, Hales Franciscan has for six consecutive years sent all its graduates -- all African-American boys, most from homes poor enough to qualify for the school lunch program -- to colleges, including Notre Dame, Northwestern, Georgetown and the Naval Academy.

``That,'' he blandly says of his career change from high finance to high school, ``is what our family does.'' After Harvard he worked as a volunteer in a migrant workers' camp in Texas. Such stuff runs in the family.

His mother saved a failing Catholic school in Chicago. His uncle, a Jesuit priest, started a school in a Hispanic neighborhood. There the students are in school four days a week and work one day. Five students share a $25,000-a-school-year job, each earning their tuitions. Ryan's sister was a sixth-year medical student at Northwestern when she left to open a medical clinic for indigent and immigrant Hispanics. With a verbal shrug, Ryan says, ``That's what we're supposed to do.''

Now he is seeking a rendezvous, of sorts, with Jon Corzine. Ryan is campaigning for the Republican nomination for the Senate seat held by Peter Fitzgerald, a Republican who is retiring.

Illinois has become inhospitable to Republicans. In 1988 George H.W. Bush carried Illinois 51-49. In 1992 and 1996 Bill Clinton carried it 49-34 and 54-37. In 2000 Al Gore carried it 55-43. To win in 2004, Ryan probably will have to run far ahead of President Bush. Asked how he plans to do that, he mentions ``the ideas of John Locke.'' If that is plan A, what, you may well wonder, is plan B?

Actually, he favors the basic Republican agenda -- limited government, personal responsibility, strong national defense. But he is, above all, a moralist who hopes to get the state exercised about the fact that 410,000 of its children -- 270,000 of them in Chicago -- are in failing schools, as such schools are defined by the No Child Left Behind law.

What, he asks, will become of these children if they reach adulthood and ``all they have is their brawn and their hands''? When he returns to walk the spotless halls of Hales Franciscan, crowds of boys embrace him, and are rewarded by being asked what their SAT scores are, and being told they are not high enough. The SAT prep course was recently canceled. For Ryan, doing something about that takes immediate precedence over campaigning.

His campaign bears watching because of what it will say about the ability of a Republican to make inroads among African-Americans. If he cannot do it, it really is hopeless.

Win or lose, this probably will not end happily. Ryan has a three-to-one lead over his nearest rival in polling of Republicans likely to vote in the March 16 primary. But in the general election he probably will learn the futility -- with few exceptions -- of asking African-Americans to vote for any Republican, regardless of his views or record, and he probably will lose in this increasingly Democratic state.

Or he will win and, being intelligent and impatient, will hate life in the Senate, where grandees like Ted Kennedy, for whom public schools are distant rumors, get away with blocking school choice for poor inner-city children. The story Ryan is trying to write -- doing well in his campaign, then doing good in Washington -- is too good to be true.